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Livestock Health, Management and Production › Animal Health Management › Review of tools available
for disease control
Animal Health Management
Review of tools available for disease control
Author: Dr Mary-Louise Penrith.
Licensed under a Creative Commons Attribution license.
TOOLS FOR DEALING WITH A DISEASE EMERGENCY
Quarantine
When a serious infectious disease is suspected in a population of animals, the area or premises is usually
quarantined pending confirmation of the disease in order to prevent spread. The area may be a farm, a
district or a larger area, depending on the time lapse between discovery of the disease and its initiation,
as well as the density and distribution of the susceptible animal population and the level of contact within
and between herds or flocks. The way in which the disease is transmitted also influences the size of the
area that will need to be quarantined. Fortunately, warm dry climates do not favour aerosol transmission
of pathogens, so this is generally not an important consideration in sub-Saharan Africa. If a single farm is
involved the farmer is usually served with a quarantine order that requires him/her not to move any
animals or their products off the premises; other restrictions may be required depending on the disease
and the circumstances. When larger areas are quarantined, road blocks are usually put in place to
prevent movement out of the area. This often requires the participation of law enforcement agencies like
the police or the army, unless the veterinary services have sufficient resources to maintain the
roadblocks, which have to operate 24 hours a day in order to be effective.
If laboratory testing does not confirm the suspicion of the disease, the quarantine is lifted. If disease is
confirmed, the quarantine will be maintained until further steps towards control have been taken or, in the
case of mild disease without a carrier state, the disease has run its course and no further infections are
expected. This was the case with pig herds that were infected with the novel pandemic H1N1 virus
(incorrectly called ‘swine ‘flu’) in 2009, when they were infected by workers with active disease. However,
most often the animals are likely to be destroyed unless there are circumstances that make that
impractical as discussed below.
Movement control
Movement control is not only an emergency disease control measure. In many countries movement
control is routinely applied, for example to animals being moved to abattoirs for slaughter, in order to
prevent illegal movements of animals that may, for example, have been introduced illegally from another
country or from an infected area in the same country. The law may make provision for movement control
of particular species, for example buffaloes or wildebeest (gnu), because they are known to be reservoirs
of diseases that can affect livestock. Movement of pigs from accredited farms in the ASF control area in
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Livestock Health, Management and Production › Animal Health Management › Review of tools available
for disease control
South Africa, as well as movement of warthogs, is subject to veterinary permits, as is movement of all
cloven-hoofed animals from the area around the Kruger National Park and currently from a wider area
since Soth Africa lost its FMD-free status after the outbreaks in KwaZulu-Natal in 2011.
When there is an outbreak of a highly infectious or trade-sensitive disease, movement control may be
more rigorously applied and, as indicated above, may involve the police and even the army, as occurred
during the Type O FMD outbreak in KwaZulu-Natal in 2000. Although it is an important and necessary
measure, movement control is far from infallible, as animal movement is not always restricted to main
roads or to roads at all, and animal products are relatively easily concealed. Careful examination of all
vehicles may be impractical along roads with heavy traffic. The effectiveness of road blocks also depends
on the commitment of the people manning them. During the first ASF outbreaks in Benin in 1997/1998 the
rate of recovery of pigs and pork at road blocks increased remarkably when meat traders, who were out
of business and annoyed about it, became involved in the road blocks and were serious about searching
for pork. The fate of animals and their derivatives confiscated at road blocks also needs to be carefully
controlled to ensure that they are not illegally traded.
Stamping out (culling)
Culling, or stamping out, of infected animal populations is a traditional way of eradicating a disease
outbreak as quickly and effectively as possible. Countries that wish to regain FMD-free status after an
outbreak in a free zone can do so much more rapidly if stamping out is used as opposed to other less
drastic approaches, like vaccination. However, there are various circumstances that can make culling less
effective, and can even result in enhanced spread of the disease. Circumstances that can lead to the
disease being widespread with multiple foci include late diagnosis, bureaucratic delays in implementation
of control measures, and logistically difficult areas, e.g. mountainous or flooded areas. The issue of
compensation has a strong influence on the effectiveness of culling. Compensation that is not market
related, or no compensation, are likely to result in disobedience and animals being concealed or illegally
moved, while compensation that is too generous may lead to dishonesty, as was reported to have
happened during the FMD outbreaks in the United Kingdom in 2001. Even when the ‘price is right’, as
was the case in Botswana when 320,000 cattle were killed during the CBPP outbreak and during the
2005 CSF outbreak in South Africa, animal owners do not like to have their animals killed and, while
cattle are difficult to conceal, concealment of pigs in the Eastern Cape Province was reported to occur.
Before embarking on massive culling, disposal of the carcasses has to be carefully planned. There are
concerns about both environmental pollution, as was reported when thousands of cattle and pigs were
culled to eradicate an outbreak of FMD in Korea in 2010 and rivers became polluted, and about spread of
infection owing to access to the sites by poor people to whom the destruction of meat is
incomprehensible.
Massive culling as a way to eradicate outbreaks is increasingly being questioned. The sight of piles of
carcasses being burned in the UK as a result of culling for both BSE and FMD caused public outrage, as
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Livestock Health, Management and Production › Animal Health Management › Review of tools available
for disease control
did the situation in South Korea, where animals were reported to have buried alive. Disposal of carcasses
is likely to become more and more of a challenge in an increasingly densely populated world, and the
psychological effects of this approach on animal owners also need to be considered. The latter was
highlighted by the fact that some affected farmers in the UK in 2001 committed suicide. There are
therefore ongoing initiatives to find alternative but effective ways of controlling animal disease outbreaks.
These place an emphasis on vaccination as well on much more rigorous preventive measures so that
outbreaks can be avoided as far as possible. Sometimes it is recognised that culling is not the right
approach; massive culling is usually not even attempted in poor countries if there are insufficient
resources to compensate the farmers. The authorities will at most attempt modified stamping out, where
only infected animals are killed and those that escape infection or recover are allowed to live. This
approach was to an extent used in Mauritius during the 2007 ASF outbreak, which was nevertheless
eradicated by 2008. It is likely that in spite of the fact that massive culling is still recommended as a
control measure, its acceptability will be increasingly questioned on the grounds of animal, human and
environmental welfare, with a growing need to take cognizance of considerations like environmental
pollution and the destruction of large amounts of edible protein in a hungry world.
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